Datasheet

V850ES/JG3-H, V850ES/JH3-H CHAPTER 20 CAN CONTROLLER
R01UH0042EJ0500 Rev.5.00 Page 1004 of 1513
Aug 12, 2011
In the receive-only mode, no message frames can be transmitted from the CAN module to the CAN bus. Transmit
requests issued for message buffers defined as transmit message buffers are held pending.
In the receive-only mode, the CAN transmission pin (CTXD0) in the CAN module is fixed to the recessive level.
Therefore, no active error flag can be transmitted from the CAN module to the CAN bus even when a CAN bus error is
detected while receiving a message frame. Since no transmission can be issued from the CAN module, the transmission
error counter the C0ERC.TEC7 to C0ERC.TEC0 bits are never updated. Therefore, a CAN module in the receive-only
mode does not enter the bus-off state.
Furthermore, ACK is not returned to the CAN bus in this mode upon the valid reception of a message frame. Internally,
the local node recognizes that it has transmitted ACK. An overload frame cannot be transmitted to the CAN bus.
Caution If only two CAN nodes are connected to the CAN bus and one of them is operating in the receive-only
mode, there is no ACK on the CAN bus. Due to the missing ACK, the transmitting node will transmit
an active error flag, and repeat transmitting a message frame. The transmitting node becomes error
passive after transmitting the message frame 16 times (assuming that the error counter was 0 in the
beginning and no other errors have occurred). When the message frame is transmitted for the 17th
time, the transmitting node generates a passive error flag. The receiving node in the receive-only
mode detects the first valid message frame at this point, and the VALID bit is set to 1 for the first time.
20.13.2 Single-shot mode
In the single-shot mode, automatic re-transmission as defined in the CAN protocol is switched off. (According to the
CAN protocol, a message frame transmission that has been aborted by either arbitration loss or error occurrence has to
be repeated without control by software.) All other behavior of single-shot mode is identical to normal operation mode.
Features of single-shot mode can not be used in combination with normal mode with ABT.
The single-shot mode disables the re-transmission of an aborted message frame transmission according to the setting
of the C0CTRL.AL bit. When the AL bit is cleared to 0, re-transmission upon arbitration loss and upon error occurrence is
disabled. If the AL bit is set to 1, re-transmission upon error occurrence is disabled, but re-transmission upon arbitration
loss is enabled. As a consequence, the C0MCTRLm.TRQ bit in a message buffer defined as a transmit message buffer is
cleared to 0 by the following events.
• Successful transmission of the message frame
• Arbitration loss while sending the message frame (AL bit = 0)
• Error occurrence while sending the message frame
The events arbitration loss and error occurrence can be distinguished by checking the C0INTS.CINTS4 and
C0INTS.CINTS3 bits, and the type of the error can be identified by reading the C0LEC.LEC2 to C0LEC.LEC0 bits of the
register.
Upon successful transmission of the message frame, the transmit completion interrupt the CINTS0 bit of the C0INTS
register is set to 1. If the C0IE.CIE0 bit is set to 1 at this time, an interrupt request signal is output.
The single-shot mode can be used when emulating time-triggered communication methods (e.g., TTCAN level 1).
Caution The AL bit is only valid in single-shot mode. It does not affect the operation of re-transmission upon
arbitration loss in other operation modes.